U.S. patent application number 16/489020 was filed with the patent office on 2020-01-02 for method for managing pinking in a controlled-ignition internal combustion engine.
The applicant listed for this patent is Continental Automotive France, Continental Automotive GmbH. Invention is credited to Olivier FORTI, Alexandre HAGUET.
Application Number | 20200003136 16/489020 |
Document ID | / |
Family ID | 58993066 |
Filed Date | 2020-01-02 |
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United States Patent
Application |
20200003136 |
Kind Code |
A1 |
FORTI; Olivier ; et
al. |
January 2, 2020 |
METHOD FOR MANAGING PINKING IN A CONTROLLED-IGNITION INTERNAL
COMBUSTION ENGINE
Abstract
A method for managing knock in a cylinder of an internal
combustion engine, in a system including at least one acoustic
sensor and a processor, in order to take into account acoustic
pollution resulting from a noise, the method including: forming and
digitizing the signals of the acoustic sensor, applying a bandpass
filter to obtain a filtered noise, determining an adjustable
gain-correction function using a gain-correction curve and,
depending on the angular position of the end of injection, the
point on the gain-correction curve to be used to convert the
filtered noise into a corrected knock score, comparing a corrected
knock score thus obtained to a knock decision threshold, to correct
the timing advance, the gain-correction curve being defined by a
calibration value and four angular points obtained by calculation
based on the start and end positions of a knock-observation window
and on a known characteristic of the noise.
Inventors: |
FORTI; Olivier; (Osny,
FR) ; HAGUET; Alexandre; (Cergy, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Continental Automotive France
Continental Automotive GmbH |
Toulouse
Hannover |
|
FR
DE |
|
|
Family ID: |
58993066 |
Appl. No.: |
16/489020 |
Filed: |
March 14, 2018 |
PCT Filed: |
March 14, 2018 |
PCT NO: |
PCT/FR2018/050607 |
371 Date: |
August 27, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/46 20130101;
G01L 23/227 20130101; F02D 41/2416 20130101; F02D 2041/288
20130101; F02D 41/28 20130101; F02D 35/027 20130101; G01L 23/222
20130101; F02P 5/152 20130101; F02D 2041/1432 20130101 |
International
Class: |
F02D 35/02 20060101
F02D035/02; F02D 41/28 20060101 F02D041/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2017 |
FR |
1752457 |
Claims
1. A method for managing knock in a cylinder of an internal
combustion engine, the method being implemented in a system
comprising at least one acoustic sensor and a processor, the method
being intended to take into account acoustic pollution resulting
from a known repeatable parasitic noise of variable temporal
position, the method comprising: forming and digitizing signals
delivered by the acoustic sensor, applying a bandpass filter in
order to preserve only a frequency range of interest for knock, in
a filtered noise, determining an adjustable gain-correction
function using a gain-correction curve, intended to decrease the
influence of the parasitic noise, determining, depending on an
angular position of an end of injection, a point on the
gain-correction curve to be used to convert the filtered noise into
a corrected knock score, comparing corrected knock score thus
obtained to a knock decision threshold, deducing therefrom an
ignition timing advance correction value to be applied in the next
cycle, wherein the gain-correction curve is defined by a
calibration value (Gin) and four angular points (A, B, C, D), said
four angular points being obtained by calculating, based on the
start and end positions (WS1, WS2) of a knock-observation window
and at least one known characteristic of the noise, the calibration
value (Gin) being a gain value at which the decrease is the
greatest representing a bottom plateau of the gain-correction curve
between the second and third angular points (B, C), and the
gain-correction curve taking the value 1 for points prior to the
first angular point (A) and for points subsequent to the fourth
angular point (D).
2. The method as claimed in claim 1, wherein the four angular
points are calculated based on a characteristic (Tbr) of the
duration of the noise and on a characteristic (Ttr) of a
transmission time of the noise to the acoustic sensor, these two
values being taken to be known characteristics of the noise.
3. The method as claimed in claim 1, wherein the parasitic noise is
a noise of injector closure.
4. The method as claimed in claim 1, wherein a transmission time
(Ttr) of the noise is obtained from a set of transmission-time
parameters, one parameter for each (cylinder at end of injection,
cylinder in which combustion is in progress) pair.
5. The method as claimed in claim 1, wherein, to calibrate the
calibration value (Gin), a simple two-dimensional calibration
depending on engine load and engine speed is used.
6. The method as claimed in claim 2, wherein the four angular
points (Xa, Xb, Xc, Xd) are calculated as follows:
Xa=WS1-(Tbr+Ttr)*6*RPM Xb=WS1-(Ttr)*6*RPM Xc=WS2-(Tbr+Ttr)*6*RPM
Xd=WS2-(Ttr)*6*RPM, WS1 and WS2 being the start and end positions
of the knock-observation window, expressed in degrees of rotation
of the crankshaft, respectively, Tbr being a characteristic of the
duration of the noise expressed in seconds, Ttr being a
characteristic of the transmission time of the noise to the
acoustic sensor expressed in seconds, RPM being the engine speed
expressed in revolutions per minute.
7. The method as claimed in claim 1, wherein the knock-decision
threshold (KTC) is determined by the expression: KTC=G*KT+1-G,
where: KT is the threshold in the absence of noise, and G is the
value on the correction curve at the point of the angle of closure
of the injector.
8. The method as claimed in claim 1, wherein the method is carried
out in real-time, for each cylinder and in each cycle.
9. A system for managing knock in a cylinder of an internal
combustion engine, the system comprising at least one acoustic
sensor and a processor, and configured to implement the method as
claimed in claim 1.
10. The method as claimed in claim 2, wherein the parasitic noise
is a noise of injector closure.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase Application of
PCT International Application No. PCT/EP2018/050607, filed Mar. 14,
2018, which claims priority to French Patent Application No.
1752457, filed Mar. 24, 2017, the contents of such applications
being incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to methods for detecting and
evaluating a level of knock in a cylinder of a controlled-ignition
internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] In controlled-ignition engines, a spark-plug spark is
generated by an electrical pulse controlled by an electronic
processor, this pulse being positioned with respect to the top dead
center to cause ignition with a certain timing advance.
[0004] In certain cases, the compressed mixture may be subject to
auto-ignition, which effect is to be avoided.
[0005] If the timing advance is too great or if auto-ignition
occurs, the effect known as knock may be observed.
[0006] For this reason, engine control systems now incorporate a
knock-detection function, based on an acoustic, and in particular
piezoelectric, sensor installed on the cylinder casing.
[0007] The presence of significant signals in a certain frequency
range, typically between 5 kHz and 25 kHz, is characteristic of the
presence of such a knock effect. If knock is detected, then the
ignition timing advance must be decreased.
[0008] However, the detection of the knock effect may be polluted
by parasitic auxiliary noises. For example, it has been discovered
that the closure of an injector generates a noise that comprises
frequency components in the spectral range of interest for
knock.
[0009] Depending on the various operating conditions of the engine,
the angular position of the closure of each injector varies.
[0010] To detect knock, for each cylinder, provision is generally
made for an observation time window, in order to remove parasitic
noises that do not coincide temporally with the moment at which
knock may appear.
[0011] However, under certain engine operating conditions, the
noise of an injector closing may `fall` in the observation time
window and may cause non-detections or wrongful detections.
[0012] Document US2012192835A1, incorporated herein by reference,
proposes a solution aiming to decrease this problem. However, in
the case where the angular position of the closure of the injector
varies rapidly or discontinuously, there remain cases of
non-detection and/or cases of wrongful detection.
[0013] Document WO 03/040677A1, incorporated herein by reference,
relates to a method for suppressing noise interfering with
detection of knock in an internal combustion engine. The knock
sensor is connected in a known way to an evaluating integrated
circuit via an input circuit. In the knock-sensor-evaluating
integrated circuit, the high-frequency sensor signal is amplified,
filtered and, during an observation period (measurement time
window), integrated. The concept on which this document is based is
that the sound transmitted by a structure, and that comes from an
identifiable source of interference, such as an injector valve, is
used to determine a signal correction value that is subtracted from
the integral value of the signal of the shock sensor, so that only
the sound due to knock is evaluated.
SUMMARY OF THE INVENTION
[0014] There is therefore a need to improve existing solutions in
order to provide a method for evaluating knock that is not affected
by the fact that a parasitic noise (such as the noise of injector
closure) may `fall` in the knock observation time window.
[0015] To this end, a method is here proposed for managing (namely
detecting/evaluating/correcting) knock in a cylinder of an internal
combustion engine, the method being implemented in a system
comprising at least one acoustic sensor and a processor (processing
unit), the method being intended to take into account acoustic
pollution resulting from a known repeatable parasitic noise of
variable temporal position, the method comprising: [0016] forming
and digitizing the signals delivered by the acoustic sensor, [0017]
applying a bandpass filter in order to preserve only the frequency
range of interest for knock, in a filtered noise, [0018]
determining an adjustable gain-correction function using a
gain-correction curve, intended to decrease the influence of the
parasitic noise, [0019] determining, depending on the angular
position of the end of injection, the point on the gain-correction
curve to be used to convert the filtered noise into a corrected
knock score, [0020] comparing a corrected knock score thus obtained
to a knock decision threshold, [0021] deducing therefrom an
ignition timing advance correction value to be applied in the next
cycle,
[0022] characterized in that the gain-correction curve is defined
by a calibration value and four angular points, said four angular
points being obtained by calculating, based on the start and end
positions of the knock-observation window and at least one known
characteristic of the noise, the calibration value (Gin) being a
gain value at which the decrease is the greatest representing the
bottom plateau of the gain-correction curve between the second and
third angular points (B, C), and the gain-correction curve taking
the value 1 for points prior to the first angular point (A) and for
points subsequent to the fourth angular point (D).
[0023] By virtue of the above arrangements, it is possible to very
greatly decrease the influence of a parasitic noise that falls in
the observation window, without substantially modifying the
pre-existing software structure. The use of the gain G lower than
1, instead of an offset as described in document WO 03/04677A1,
allows the dispersion of the results to be decreased by a factor G,
this having no impact on the dispersion/score ratio since the gain
G is also applied to the score. In contrast, the coefficient G is
also applied to the threshold of detection of knock, which is not
the case in the offset method. A curve of the ratio between the
dispersion and the threshold would show that this ratio in the gain
case is always lower than the ratio in the offset case. The zone of
uncertainty about the detection threshold is therefore smaller with
the gain and the quality of the detection is improved thereby.
[0024] The gain correction is applied immediately with no delay
when the injected closure varies rapidly or in hops and falls in
the observation window.
[0025] In various embodiments of the invention, there may possibly
furthermore be recourse to one and/or the other of the following
provisions:
[0026] According to one option, the four angular points are
calculated based on a characteristic of the duration of the noise
and on a characteristic of the transmission time of the noise to
the acoustic sensor, these two values being taken to be known
characteristics of the noise.
[0027] Advantage thus obtained: knowing only two parameters
relative to the parasitic noise, it is possible to construct the
correction curve that will allow the effect of this parasitic noise
to be attenuated.
[0028] According to one option, the parasitic noise in question is
a noise of injector closure. It turns out that this noise is
sometimes preponderant because it comes from a nearby source,
fastened directly to the cylinder casing.
[0029] In practice, it is a question of the noise of closure of the
injector of the following cylinder in the cycle, i.e. the cylinder
that follows the cylinder in which combustion is in progress in the
operating sequence of the engine.
[0030] According to one option, the transmission time of the noise
is obtained from a set of transmission-time parameters, one
parameter for each (cylinder at end of injection, cylinder in which
combustion is in progress) pair. Advantageously, the geometric
configuration on the engine is thus taken into account by way of
these transition times, which may be different for each pair of
successive cylinders in the sequence.
[0031] According to one option, a linear interpolation is used to
obtain the values of the correction curve between the first and
second angular points, and between the third and fourth angular
points. Advantageously, this simple calculation is very rapid and
utilizes very few of the resources of the microcontroller.
[0032] According to one option, to calibrate the calibration value,
a simple two-dimensional calibration depending on engine load and
engine speed is used. Advantageously, this calibration is simple
and consumes very little memory.
[0033] According to one option, the calibration values are
comprised between 0.25 and 1.
[0034] According to one option, the calibration values decrease as
the engine load increases.
[0035] According to one option, the abscissae Xa, Xb, Xc, Xd of the
four angular points are calculated as follows:
Xa=WS1-(Tbr+Ttr)*6*RPM
Xb=WS1-(Ttr)*6*RPM
Xc=WS2-(Tbr+Ttr)*6*RPM
Xd=WS2-(Ttr)*6*RPM
[0036] where: [0037] WS1 and WS2 are the start and end positions of
the knock-observation window, expressed in degrees of rotation of
the crankshaft, respectively, [0038] Tbr is a characteristic of the
duration of the noise expressed in seconds, [0039] Ttr is a
characteristic of the transmission time of the noise to the
acoustic sensor expressed in seconds, [0040] RPM is the engine
speed expressed in revolutions per minute.
[0041] According to one option, the knock decision threshold KTC is
determined by the expression KTC=G*KT+1-G, where: [0042] KT is the
threshold in the absence of noise, and [0043] G is the value on the
correction curve at the point of the angle of closure of the
injector.
[0044] According to one option, the method is carried out in
real-time, for each cylinder and in each cycle. Advantageously,
there is no delay in taking into account changes; for example, if
the injector closure hops by an angle, the new situation is taken
into account immediately.
[0045] According to one option, the passband of the bandpass filter
is [5 kHz-25 kHz]. Thus, advantageously, any noise that is located
outside of this band is eliminated.
[0046] An aspect of the invention also relates to a system for
managing knock in a cylinder of an internal combustion engine, the
system comprising at least one acoustic sensor and a processor,
characterized in that the latter is configured to implement the
method such as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] Other features and advantages of aspects the invention will
become apparent from the following description, which is given by
way of nonlimiting example with reference to the appended drawings,
in which:
[0048] FIGS. 1 and 1A schematically show the system and components
in which the method according to an aspect of the invention is
implemented,
[0049] FIG. 2 shows an illustrative timing diagram,
[0050] FIG. 3 illustrates the gain-correction curve,
[0051] FIG. 4 illustrates a two-dimensional correction map,
[0052] FIG. 5 shows a schematic block diagram of the
correction-calculating process,
[0053] FIG. 6 shows a diagram illustrating the steps of the
method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] In the various figures, the same references have been used
to reference identical or similar elements. For the sake of clarity
of the description, certain temporal elements are not shown to
scale.
[0055] In FIG. 1, a processor 1 for managing a combustion engine,
typically a gasoline internal combustion engine, has been
shown.
[0056] The illustrated example is based on a four-cylinder engine,
but the method may equally well be applied to a three-cylinder
engine, or even to a six-cylinder in-line or V engine.
[0057] It will be noted that an aspect of the invention could be
applied to a liquid-petroleum-gas (LPG) engine, and more generally
to any controlled-ignition internal combustion engine.
[0058] Each of the cylinders is equipped with a fuel injector with
an injection nose that opens directly into the combustion chamber:
an injector 31 in the first cylinder CYL C1, an injector 32 in the
second cylinder CYL C2, an injector 33 in the third cylinder CYL
C3, and an injector 34 in the fourth cylinder CYL C4.
[0059] On the cylinder casing 4 (also called the "engine block") a
knock sensor 2 is installed, which is connected by a cable, in
general a shielded cable, to the engine processor. This sensor is
an acoustic sensor and preferably a piezoelectric sensor; it is
configured to be sensitive to the vibrations produced in the
cylinder casing. It will be noted that the engine block 4 may be
made of cast iron or of aluminum alloy.
[0060] In the illustrated example, the cylinder casing is equipped
with a single acoustic knock sensor, but it could have a plurality
thereof; in the case of motors comprising two rows of cylinders
such as for example six-cylinder V or V6 engines or eight-cylinder
V or V8 engines, there will be at least two knock sensors, one per
row of cylinders.
[0061] As is known per se, the operation of the engine is based on
a time-ordered sequence (admission, compression, combustion,
exhaust) implemented in each of the cylinders, the successive order
of the cylinders being set by design. In the illustrated example of
the four-cylinder engine, the conventional order of ignition is CYL
C1-CYL C3-CYL C4-CYL C2.
[0062] As known per se, the angular position of the crankshaft
(generically referenced by .phi.) is known by virtue of a toothed
or coded target 14, with a sensor 11 of position of the engine
flywheel.
[0063] FIG. 2 illustrates a timing diagram that shows at the bottom
a time segment centered on the combustion in cylinder N (CYL N) and
that shows at the top the phase of injection of gasoline into the
following cylinder in the sequence, which cylinder is referenced
N+1.
[0064] In the cylinder N+1, an electrical signal 36 controlled by
the processor causes the injector to open at the angular position
.phi.Op and the injector to close at the angular position .phi.Cl.
This closure causes acoustic waves; in other words a noise that
will propagate throughout the cylinder casing. As already mentioned
in the introduction, the noise of this closure may coincide
temporally with the window WS for observing knock in the cylinder
N.
[0065] This observation window starts at the angular position WS1
and ends at the angular position WS2. The start WS1 of the
observation window and the end WS2 of the observation window WS are
the result of a pre-existing calibration that is known per se and
not described in detail here.
[0066] Depending on the command 36, 37 dictated by the (mapped)
engine operating point, the noise of the injector closure may fall
just before the observation window (reference 5), it may fall so as
to straddle the start of the observation window (reference 51), it
may fall completely within the observation window (references 52),
or it may fall so as to straddle the end of the observation window
(reference 53) or after the observation window (reference 54).
[0067] It will be noted that in FIG. 2 the x-axis represents
crankshaft angular position, this also corresponding to the passage
of time, the conversion between the two being dependent on engine
speed (denoted RPM below).
[0068] It will be understood that the noise of closure of the
injector of the cylinder N+1 may therefore form a parasitic noise
with respect to observation of knock in the cylinder N.
[0069] This noise has a known duration, of about one millisecond:
the duration, which is denoted Tbr, is preferably indicated in a
calibration parameter. One specific duration may be defined for
each cylinder.
[0070] Another important feature for what follows is knowledge of
the transmission time of the noise from its source to the knock
sensor 2. This transmission time is denoted Ttr. It will be
understood, in light of FIG. 1, that the transmission times Ttr for
each cylinder are different or even very different, in particular
because of the different distances. Therefore, provision is made to
store a set of transmission-time parameters, and preferably one
parameter for each (cylinder at end of injection, cylinder in which
combustion is in progress) pair. In the illustrated example, the
number of parameters may be limited to four; however a more complex
parameterization may be employed, in particular if a second knock
sensor is used.
[0071] The inventors have observed that the noise of injection
closure is known and repeatable; the duration of this noise and the
transmission time required for it to reach the knock sensor are
simple parameters that are known in advance.
[0072] In contrast, what is not known in advance, but rather
determined in real-time in each cylinder injection cycle, is the
angular position .phi.Cl corresponding to the moment of injector
closure. This datum is calculated in real time based on a
pre-existing complex calibration (i.e. one already available and
implemented in conventional engine operation).
[0073] When the injector noise coincides partially or completely
with the knock observation window, this causes an undesirable
increase in noise level in the frequency range of interest (i.e. in
the band [5 kHz-25 kHz]).
[0074] The inventors have astutely proposed to use a
gain-correction curve 7 to greatly decrease the effects of this
undesirable increase.
[0075] This gain-correction curve makes it possible to choose,
depending on, the angle at which injected closure occurs, a gain G
that is adjusted in real time between a base value of 1 band a gain
value at which the reduction is strongest, namely Gin.
[0076] As illustrated in FIG. 3, the definition of the correction
curve is based on the determination of four angular points (A, B,
C, D).
[0077] It may be seen that this correction curve takes the value of
unity (i.e. of 1) before a first angular point denoted A (segment
71). This corresponds to the case where injector closure generates
a noise the effects of which are entirely located before the
observation window WS. This correction curve also takes a value 1
after a fourth angular point denoted D (segment 75). This
corresponds to the case where injector closure generates a noise
the effects of which are entirely located after the observation
window WS.
[0078] It may be seen that this correction curve takes the value
denoted Gin between the second angular point denoted B and the
third angular point denoted C. In this segment referenced 73, the
curve forms a plateau taking the value Gin.
[0079] It will be seen below how the calibration value Gin is
determined.
[0080] Between the first angular point denoted A and the second
angular point denoted B, the curve 7 is rectilinear 72, in other
words it is a question of a linear interpolation between the first
and second angular points. Likewise, between the third angular
point denoted C and the fourth angular point denoted D, the curve 7
is rectilinear 74, in other words it is a question of a linear
interpolation between the third and fourth angular points.
[0081] Of course, instead of a linear interpolation, a different
function taking into account the asymmetry of the noise, for
example a difference in power between the start and end of the
noise, could be used.
[0082] In FIG. 3, another example of a gain-correction curve has
been shown with a dot-dashed line referenced 7'. Specifically, it
will be noted that in each engine cycle, the limits WS1, WS2 of the
observation window may change as may the engine speed RPM. In other
words, the calculation is carried out in real-time in each
combustion cycle of one of the cylinders.
[0083] FIG. 4 illustrates the calibration table that allows the
value Gin to be obtained depending on engine operating point; it is
a question of a two-dimensional calibration 6; in other words, a
scalar value Gin is obtained in a two-dimensional space, the two
dimensions of which are engine load CHGMOT and engine speed or RPM.
This type of calibration is very commonplace and therefore not
described in more detail here.
[0084] It will firstly be noted that the values of Gin are always
lower than or equal to 1; moreover, in the illustrated example, the
values Gin are comprised between 0.25 and 1, this making it
possible to achieve a decrease by a factor of as high as four, with
a view to attenuating parasitic noise present completely in the
observation window WS. However, lower values of Gin are not
excluded.
[0085] The gain-correction curve may therefore be defined very
simply by the four points of definition with their abscissae and
their ordinates A(Xa, 1), B(Xb, Gin), C(Xc, Gin) and D(Xd, 1).
* * * * *